Coffee and Insulin – How Caffeine Intake Affects Weight Loss


How do you start your morning off? Mine begins with a steaming hot cup of my favorite coffee. The black nectar also accompanies my workouts, my busy evenings when I have to work late, my headache treatments, and even my post-workout recovery shakes. I know I am not alone in my love for coffee. In the past 6 decades, researchers have conducted more than 21,000 studies on coffee’s signature stimulant, caffeine. That’s an average of one new study a day! If there is a disease then chances are that someone has already tried to link the effects of caffeine to it. Cancers, heart disease, infertility, brain malfunction, asthma, migraines, gallbladder disease, attention-deficit hyperactivity disorder, high and low blood pressure, diabetes and obesity have all been on the list. You have probably been warned to stay away from drinking too much coffee and given tips on how to gradually get off the java, but is it worth the effort to cut back and even quit? Hold onto your mug and keep reading!

Calorie-Free Insulin Surges
The problems regarding coffee’s impact on blood sugar and insulin levels have been brewing for a while and the arguments are steaming on both sides. Short-term metabolic studies have shown that caffeine intake can acutely lower insulin sensitivity and sometimes even raise blood sugar levels. One study published in “Diabetes Care” found that consuming 70 grams of coffee grounds for 4 weeks increased fasting insulin concentrations in 40 healthy volunteers without substantially affecting fasting glucose concentrations. The researchers suggested that such results reflect decreased insulin sensitivity from high caffeine intake. What’s worse is that after just 5 days of regular supplementation, the body’s blood glucose control system may become tolerant to the effects of caffeine. If, for whatever reason, you would want to get off the bean, be aware that a sudden withdrawal can cause severe headaches, irritability, anxiety, depression, drowsiness and fatigue.

Should you worry? Absolutely not! A growing body of evidence suggests that a habit of drinking a lot of coffee every day is associated with higher insulin sensitivity and a lower risk for type-2 diabetes. After analyzing data on 126,000 people for as long as 18 years, Harvard researchers calculated that when compared to people who do not partake in drinking coffee, those who consume 1-3 cups of caffeinated coffee daily can reduce their diabetes risk by up to 10%. Having 6 cups or more each day slashed men’s diabetes risk by 54% and women’s by 30% over people who don’t drink coffee.

Coffee’s way of life once it gets into our bodies is very interesting. You enjoy your favorite cup of java and for a few hours after you feel energized, awake and happy while burning up extra fat stores and being in the insulin resistant state. If you repeat this morning java habit day in and day out, within several months to a few years, your insulin sensitivity is heightened and your risk of developing type-2 diabetes goes down significantly. How can we explain this? Coffee has caffeine, but its effects are somewhat different from the pure chemical. The beans are loaded with antioxidants, a group of compounds called quinines, tocopherols, and magnesium, all of which are shown to improve glucose metabolism and the body’s response to insulin in clinical settings. Chlorogenic acid (also found in blueberries) and trigonelline (also found in peas, lentils, soybeans, and sunflower seeds) are two of the major phytochemicals in coffee and have been shown to decrease blood glucose and insulin concentrations in the blood compared to a placebo after ingesting sugar. It is likely that these two powerhouses increase insulin sensitivity. Wow, way to go coffee!

Jacked Up Workouts
Coffee and other drinks with its active stimulant caffeine (or the herbal counterpart Guarana) can help delay fatigue, contribute to increased alertness and faster reaction time. This provides an outstanding mental boost which is famous for helping athletes through vigorous training sessions. Science has established that caffeine has numerous physiological and psychological effects on the central nervous system and it easily crosses the blood-brain barrier where it blocks the relaxing neurotransmitter adenosine by binding to its receptors on the surface of cells without activating them. By doing so, caffeine “excites” the nervous system and has been shown to numb the pain, increase heart rate and stimulate the release of adrenal hormones (epinephrine, norepinephrine and cortisol) which may help you crank up your workout intensity and get that last extra rep while postponing fatigue, decreasing the perceived difficulty of the exercise and allowing you to leave the gym without feeling exhausted. This is why I add a couple of espresso shots to my pre-workout shake!

Although caffeine is not a carbohydrate and has zero calories, it does stimulate the pancreas to secrete a small amount of insulin, particularly if you are prone to insulin resistance and hyperinsulism. The reason this happens is because drinking coffee enhances the effect of two hormones, adrenaline and glucagon, which release stored sugar (glycogen) from the liver and a small amount of energy from fat stores resulting in higher blood sugar and elevated insulin. By this mechanism, caffeine decreases insulin sensitivity. However, this happens only for a brief period of time and is a normal biological response. Adrenaline and glucagon also go up when you are stressed or during exercise. Even a simple walk will decrease insulin sensitivity, but nobody has had insulin resistance from exercising. If anything, physical activity is praised for its impact on adrenaline and noradrenaline since these chemical messengers get body fat moving from stored places to the bloodstream. From here, it’s a short trip for the fat to get out of the system and then you can easily use it as fuel. As it turns out, the caffeine-induced insulin resistance is just a result of increased circulating free fatty acids which can be burned off during your workout. For that matter, coffee has been used for years by endurance athletes, bodybuilders, boxers, powerlifters and other athletes. It has been researched as an excellent thermogenic, which is a type of supplement which may help burn body fat.

In case all of the above benefits are not enough justification for you to enjoy a hot cup of Joe, here is another important reason why you may want to add a cup into your workout arsenal. A caffeinated body may burn calories at a higher rate! The black nectar gives you a nice punch at the gym, so your intensity is super high, plus it stimulates a cascade of hormones that release free fatty acids into the bloodstream causing the body to burn fat while sparing carbohydrates to use as energy. Subjects who consumed 300 mg of caffeine 2 hours before exercising on a stationary bike for 30 minutes were not only able to workout at a higher intensity, but they also used a much greater percentage of body fat for fuel. Another study found that the caffeine in 2 cups of coffee may cause an average woman to expend up to 50 extra calories over the course of 4 hours. The important part here is exercise which is not a revelation, I know, but it’s an important point. Nobody loses fat using caffeine supplements alone and you are much better off drinking coffee before your intense workouts than drinking a cup while sitting on the couch watching TV.

One terrific thing you can get from training while on some caffeine is that the temporary dip in insulin sensitivity primes the body to become even more responsive to nutrient intake afterwards. Think about it this way. When you train, the body wants to get rid of fuel from fat cells, but also increase its ability to take in and replace what is lost as fast as possible afterwards. The fat cell’s “machinery” is not designed to store and release fuel at the same time, which would be counter-productive. Put differently, during training and after caffeine ingestion, you are in an insulin resistant state which is replaced by an insulin sensitive state once the activity or the action of the caffeine stops. This premise is the reason why you are advised to refuel within an hour after finishing a workout since muscle cells become extremely sensitive to insulin and the nutrients carried by the hormone, and thus, can soak up the food like a sponge.

Regardless of whether you train in the caffeinated state or not, exercise itself reduces the detrimental effects of caffeine. A body in motion depends on a special metabolic pathway, called non-insulin dependent glucose uptake, which literally negates any insulin-related disturbances caused by the stimulant. You already know that nothing beats a good workout for fat loss and muscle gain. So, bodybuilders shouldn’t worry about their stimulants or insulin fluctuations from consuming caffeine. As a matter of fact, caffeine can serve them well in helping store glycogen which is the primary fuel for muscle.

Java-Spiced Recovery
For the first time, researchers from the Garvan Institute of Medical Research in Sydney, Australia showed that a small group of 7 well-trained endurance cyclists who ingested caffeine (8 mg per kilogram of body weight which is the equivalent of drinking 5-6 cups of strong coffee) along with a carbohydrate had 66% more glycogen in their muscles 4 hours after finishing intense, glycogen-depleting exercise, compared to when they consumed carbohydrate alone. For the entire 4-hour recovery period, the caffeinated drink resulted in higher levels of blood glucose and plasma insulin. “If you have 66% more fuel for the next day’s training or competition, there is absolutely no question you will go farther or faster,” said Dr. Hawley, the study’s senior author. Researchers also noted that 1 hour after exercise, muscle glycogen levels had replenished to the same extent whether or not the athletes had the drink containing carbohydrates and caffeine or carbohydrates only. It looks like coffee may supply a longer-lasting effect to carry you through your next workout.

Now, that may seem like a breakthrough concept, but here’s the deal. Let’s not discredit the fact that the number of participants in the research study was rather small, the caffeine dose was very high, and most of us do not ride in the same highly trained bike camp. Additionally, nobody is going to achieve that level of glycogen absorption within a day after a workout. I think that the only reason for you to add caffeine to your post-workout meal would be if you are going to exercise again within 4 hours after the first workout. Even if you’re training every day, you have 24 hours to replenish your carbohydrate stores and there’s no essential need to dump a bunch of caffeine into your system. By the way, the overall intake of nutrients is much more important for recovery than the amount of caffeine or the time it was taken.

With that said, although it won’t help you store more fuel and you will still end up with the same amount of glycogen in the muscles, caffeine might expedite the process and thus jump-start the recovery process after training. Better yet, moderate doses of caffeine have shown to cut post-workout muscle soreness by up to 48%, according to a study published in “The Journal of Pain“. Drinking just 2 cups of coffee 1 hour before exercise appeared to be more effective than several commonly used pain relievers (aspirin and naproxen) which produced a 25% and 30% reduction in soreness, respectively. Ibuprofen has produced inconsistent results. If you are fine with drinking a few cups of coffee before and after training and find pleasure in running on all cylinders while still being able to fall asleep by midnight, I say go for it!

Coffee With Meals
While caffeine intake certainly won’t make you fat, insulin resistant or diabetic, it may increase your glucose and insulin response to meals which may thwart the effects of your hardcore training. Coffee, by itself, has a pleasant bitter taste, but its aroma really comes out when you have something sweet and fatty with it, like frothed milk and a doughnut. It sure tastes good, but the effect is only short-lived. So, eating that dessert with coffee may tend to pack on the pounds and make you insulin resistant if you don’t exercise. In sedentary individuals, especially those with a traditional Western diet that is high in sugar and saturated fats, elevated concentrations of circulating epinephrine and free fatty acids in response to caffeine may negatively affect glucose tolerance and drive insulin and blood sugar up after meals. In one study, subjects who ingested a sugary beverage after a high-fat meal, had their blood glucose levels increase 32% higher compared to subjects who had water in place of the high-fat meal. In the second part of the study, subjects were given 2 cups of caffeinated coffee in addition to the high-fat meal and sugary beverage. This time, blood glucose doubled and was 65% higher than in the subjects who had only water before the sugary drink.

coffee-insulin-bagelCoffee stimulates digestive juices and helps you with various unpopular food-related bloating problems. Java also relaxes the walls of the blood vessels and the airways in the lungs, elevates heart rate and metabolism and increases the force of muscular contractions.

A significant number of respectable studies prove that moderate coffee consumption doesn’t increase the risk of heart attack or cancer, contrary to false alarms in the past. In fact, it may actually do the reverse and might even help prevent Parkinson’s and Alzheimer’s diseases, as well as certain cancers due to its antioxidant properties. Caffeine is used in migraine medications and certain headache treatment formulas. It does not dehydrate the body, although this myth still circulates. Most caffeinated drinks put far more fluids into the body then take out of it.

Some people say they drink coffee for its high caffeine content. Others just love the taste, aroma, flavor, and full-bodied richness of the drink. Then there are coffee junkies who simply don’t know when and why they got hooked on java. Scientifically speaking, you can get addicted to this popular drug in the same way you can get addicted to TV, or to Twitter, your iPod, or to a certain type of ice cream. In other words, there is no such thing as biological addiction to caffeine and even at the highest possible dose, it will be metabolized and excreted within 24 hours. Still, if you’ve been drinking more coffee, tea and soda than water for a long time and then suddenly stop it altogether, expect to experience some withdrawal symptoms like headaches, fatigue, lack of energy and a drop in blood pressure. If you have some health problems and are thinking about going the decaf route, do so gradually and make sure to see your doctor to ensure that you have no other health concerns. If you are generally healthy and haven’t joined the coffee club, but used other ways of getting caffeine into your system, now is the time to change.

When it comes to insulin management and overall health and well-being, my preference would fall in favor of organic coffee over artificially produced or otherwise isolated caffeine which I would use just before training only. One study published in the 2006 “Journal of Nutrition” demonstrated that caffeine alone produced greater blood glucose and insulin levels than caffeinated coffee, and decaffeinated coffee resulted in a 50% lower glucose response than a placebo. This means that unlike its active ingredient, caffeine, coffee possesses a unique glucose and insulin sparing effect. The researchers concluded that these results help explain why chronic coffee consumption is associated with a lower rate of diabetes.

If you haven’t tasted any type of coffee that you’ve enjoyed then learn to prepare your own brew. Where do you start? With the bean, of course. Out of the nearly 100 different varieties of coffee beans, only 2 make their way to the cup. Arabica, known for its deep complex flavor, is the most popular type and accounts for about 75% of the beans sold throughout the world. Robusta is a cheaper bean usually considered a filler and often lurks in the canisters you buy in the supermarket. If you need an energy spike without calories, make your own coffee with Arabica beans, as they contain less caffeine but have plenty of other beneficial compounds not found in caffeine pills or supplements.

coffee-insulin-beansDepending on the origin of the coffee bean, coffee can have a more nutty, spicy or floral aroma along with different levels of acidity or “brightness” making them either lively or smooth. Roast color affects the richness of the coffee, making it light and crisp or full-bodied and rich. If you care about coffee, you have to grind the beans right before you make it. That’s right, buy whole beans that have been roasted within 2 weeks of purchase, put them into a grinder and grind them up. As soon as the beans are ground, the coffee oils are exposed to air which can dry them out.

A standard cup of drip coffee may have 80-150 mg of caffeine depending on the bean used, the size of your cup, how strong it is and how it is made. The French press method, for example, is known to produce more caffeine than other techniques. Real Italian espresso coffee with around 77 mg per shot produces a lower insulin response because the high pressure of steam causes the ground coffee to release its flavor in concentrated form without releasing too much caffeine at the same time. A teaspoon of instant coffee will give you about 55 mg of caffeine.

As a comparison, the average energy drink contains nearly 4 times the amount of caffeine found in commercial soda beverages ranging from 22 mg in Diet A&W Cream Soda to 118 mg in Vault Soda. Certain types of tea and chocolate may be surprisingly energizing. Java Chai, for example, contains 120 mg of caffeine per serving, while a cup of Lipton Brisk Green Tea has just 10 mg. Even some medications have caffeine. A standard dose of over-the-counter pain relievers have around 56-120 milligrams.

Caffeine is the main ingredient in the majority of diet pills and pre-workout supplements used by bodybuilders and other fitness enthusiasts. Typically, the manufacturer’s list the chemical as “Methyl Xanthines” or simple “Xanthines” and should reveal how much each pill contains, but since the industry is not regulated, don’t believe everything that’s written. If you are curious, you can find out the amount of caffeine in many different drinks here:

Another important point is that basic black coffee will do all the above provided you drink it black and avoid the foamy stuff made with milk, skim milk, soy milk, half and half, cream, non-dairy creamer, sugar, different types of sugar-free sugar, honey, syrups flavored with stuff that you can’t pronounce, powdered vanilla, chocolate, and a dozen of other additives. Stirring in just about everything known to man not only adds calories and can cause your insulin levels to spike, but also blocks the body from using previously stored sugars and fats which diminishes the metabolic effect.

Dose of Caffeine 
Several studies have found that 3-6 cups of mild coffee a day decreases your risk of type-2 diabetes by up to 50%. A team of Japanese researchers reported in the “Journal of the National Cancer Institute” that 3-4 cups of coffee daily provided greater protection against liver cancer than did 1-2 cups. The amount of caffeine that’s necessary to have a good ergogenic, or sports performance enhancing response, ranges from 3-5 milligrams per kilogram of body weight. For a small-sized bodybuilder or fitness enthusiast, that’s a lot of caffeine to have in one shot!

More is not better, either. A Dartmouth Medical School study found that 400 mg of caffeine a day (about 8 espressos) decreases insulin sensitivity by 35%. According to the American Psychiatric Association’s (APA) Diagnostic and Statistical Manual of Mental Disorders, some people can experience caffeine intoxication symptoms which includes restlessness, nervousness, excitement, insomnia, flushed face, and gastrointestinal complaints after ingesting as little as 100 milligrams of caffeine per day. At levels of 1,000 milligrams of caffeine per day, symptoms may include muscle twitching, rapid heart beats, abnormal electrical activity in the heart, and psychomotor agitation.

Picture how this applies to a real life situation. You wake up in the morning and have a large coffee. If it’s a small cup of drip coffee, you will get away with 100 mg of caffeine, but the popular “Venti” size has a whopping 480mg of caffeine! A few hours later, let’s say you have a diet soda and then another large glass of iced tea at lunch which adds an extra 72 mg per serving, at least. As the day continues, so does the caffeine drip into your system. You decide to hit the gym and ingest an explosive dose of pre-workout supplements worth of 300 mg before your workout washed down with a double-shot latte. Now, do you take a single or a double thermogenic dose for that super high intensity training session? Even at conservative levels, the life of an average bodybuilder runs on 1,000 mg of caffeine per day.

coffee-insulin-pouringTo stoke your calorie burning furnace on training days, try taking 200-400 milligrams of caffeine before a workout. Sometimes, I like to mix a few shots of fresh espresso into my whey protein shake for a nice frappuccino flavor and an awesome amino boost. If coffee is not your “cup of tea”, you can use pure caffeine tablets or take a stimulant-type supplement.

Certain experts in the field recommend to take around 100 mg of caffeine at the end of your workout when you can control which tissues soak up sugar and which ones don’t. Here, you capitalize on the insulin resistance of fat cells and the insulin sensitivity of muscles. The lean tissues can soak up nutrients like a sponge and coffee may help with that. The reason why you may skip the post-training dose is that caffeine can stay in the body for about 10 hours. If you have a fully functioning liver, don’t drink alcohol or take steroids which may extend the rate of excretion. Thus, even if you train late at night, the caffeine from your morning coffee is still going to be hanging around in your system.

The time of day also matters when drinking coffee. The full effect of caffeine reaches the bloodstream about 45 to 60 minutes after you drink a your first cup of coffee, tea, cocoa or caffeinated soda. At around 15 minutes after your first sip, your brain releases the neurotransmitter, dopamine, which enhances mental focus and leads to wakefulness peaking after about a half an hour. So, taken immediately before exercise it may do some pretty incredible things. Before bedtime, not so much.

There has been some recent talk about the effect of caffeine on the supplement creatine, the “golden nugget” of muscle growth. When you use creatine, you’re supposed to consume carbohydrates at the same time which facilitates the delivery. Since caffeine actually reduces carbohydrate uptake, you won’t be able to pull much creatine into the muscles. It’s easy to avoid this problem. Just have your coffee and creatine a few hours apart!

Side Effects: 
Too much of anything can have a negative effect, but if you understand moderation, coffee can be a good friend. Now, for a word of caution. Don’t go too crazy on caffeine or you may become jittery and nervous. Your over-the-edge mental alertness may actually lead to a loss of focus and concentration.

High levels of caffeine consumption have been associated with an increased risk of stroke, arthritis, insomnia, heart palpitations, tremors, sweating, nausea, diarrhea, chest pain, and neurological symptoms. In addition, by inhibiting the activity of vitamins folate, B12 and B6, high levels of caffeine may interfere with your body’s ability to regulate two significant cardiovascular disease risk factors, which include homocysteine and cholesterol. Since caffeine causes blood vessel constriction, it may turn into a deadly poison for people with high stress levels or high blood pressure.

Coffee’s benefits are much more profound than its side effects when consumed in moderation. It has been repeatedly shown to preserve muscle glycogen during exercise, improve exercise performance, raise metabolic rate, facilitate fat burning and increase weight loss. Don’t try to accelerate the weight loss process by sipping black coffee all day though. Three cups in a day is enough since too much caffeine can cause anxiety, nausea and headaches.

Remember, the benefits of caffeine often fade with habituation. Most studies have shown that complete tolerance to caffeine can develop after about 18 days. Does that mean that all of us who have been living on Starbucks for years are completely immune to all the proclaimed benefits? The short answer is no. In the studies referenced earlier, people were consuming 900 milligrams of caffeine per day, every single day. What happens if you “cycle” caffeine and take more on training days and less during recovery? Further research needs to be done on that. Some people are more sensitive to caffeine and other chemicals than others. From personal experience, I can say that coffee is not all that powerful. There were times when I would fall asleep within an hour of having a triple shot cappuccino, although my heart would be racing at first, and I wasn’t even sleep-deprived or sick. There were other times of mental clarity and superb physical stamina without a single milligram of caffeine in my system. Feel free to experiment a little with different caffeine dosages and see if implementing coffee into your routine helps you reach your fitness goals faster!


About Author

Elena Voropay

Elena Voropay is a Certified Personal Trainer, Fitness Instructor and Certified Nutritionist. She also holds accreditations for her knowledge in Iridology and Herbal Medicine. Elena has conducted presentations and lectured on various health, fitness and science-related topics. See my profile page for more information!


  1. Richard Karl Remmen on

    Wonderful and well researched article. Coffee, Yerba Mate, Green tea and I bet all beverages and foods with substantial caffeine content are in fact physiologically addictive. In my case, 3 days of consuming even a cup a day of the above and I’ll experience headaches, lethargy and depression if I fail to consume the same amount on the fourth day. The withdrawal symptoms only last a day or two for me. But consequently, I only consume any of these one day a week now and it’s before my weekly 3-hour weightlifting workout It really helps me get through that workout!

  2. This is a controversial topic with a plenty of science being alleged behind every claim. If you have any citations of your sources it would be nice to be able to check the original studies. In the field of nutrition, every opinioneering blogger is a scientist, including dozens of doctors with the most ludicrous claims. Thank you.

    • ShapeFit

      Hi Rostan – We will check with the author (Elena) and see if she can provide additional information regarding citations or references.

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